Typically, an injection apparatus of a molding machine moves an injection plunger forward in a sleeve using an injection cylinder to press molding material out from the sleeve into a cavity formed between a pair of mold portions. The molding material is thus injected, or supplied, into the cavity. The injection, or supply, step includes a low-speed step, a high-speed step, and a pressure-increasing step. Specifically, the injection apparatus moves the injection plunger forward at a comparatively low speed at the initial stage of injection such that the molding material does not catch air. The injection apparatus then moves the injection plunger forward at a comparatively high speed to shorten the time necessary for a molding cycle. Subsequently, to avoid sink mark formation, the injection apparatus pressurizes the molding material in the cavity with the force acting in the direction in which the injection plunger moves forward. To ensure the series of operation performed by the injection apparatus, an injection apparatus (a die cast machine) disclosed in Patent Document 1, for example, has been proposed.
As illustrated in FIG. 10, the injection apparatus of Patent Document 1 includes a hydraulic circuit. An injection, or supply, step is carried out through hydraulic pressure control in the hydraulic circuit. Specifically, in the injection apparatus, a supply accumulator 82 communicating with a gas cylinder 81 is connected to a head portion 80a of an injection cylinder 80 through a passage. A pilot check valve 84 and a speed control valve 85 are mounted in the passage. Hydraulic fluid is delivered to the supply accumulator 82 after having been pressurized to a predetermined pressure by a hydraulic pressure pump 83a. 
A pressure-increasing step accumulator 87 communicating with a gas cylinder 86 is connected to a passage connected to the speed control valve 85. A flow control valve 88 is located in a passage by which the supply accumulator 82 and the pressure-increasing step accumulator 87 are connected to the head portion 80a of the injection cylinder 80. By controlling the flow rate of hydraulic fluid through the flow control valve 88, the movement speed of a piston 80c of the injection cylinder 80 is controlled.
The injection apparatus of Patent Document 1 carries out a low-speed step and a high-speed step by supplying hydraulic fluid from the supply accumulator 82 to the head portion 80a of the injection cylinder 80 to move the piston 80c at a low speed or a high speed. The movement speed of the piston 80c is controlled by controlling the speed control valve 85. A pressure-increasing step is performed by supplying pressurized hydraulic fluid from the pressure-increasing step accumulator 87 to the head portion 80a of the injection cylinder 80. At this stage, the pressurization time is controlled by controlling the flow rate of the hydraulic fluid by means of the flow control valve 88.